20 Static Electricity 1. How many excess electrons are on a sphere with a charge of 9.20 1017 C? 2. Two charges, q1 and q2, are separated by a distance, d, and exert a force, F, on each other. Identify what new force will exist if a. q1 is doubled and q2 is cut in half. b. q1 is tripled and q2 is doubled. 7. A positive charge of 3.4 107 C exerts a repulsive force of 9.0 N on a second charge 4.0 cm away. Determine the second charge. 8. An attractive force of 0.87 N exists between a positive charge of 5.0 C and a negative charge of 1.5 C. What is the distance between the charges? c. q2 is cut in half and d is tripled. 3. An electric force of 0.030 N acts between two charges which are 7.2 cm apart. Calculate the force acting between the charges if the distance between them is reduced to 1.5 cm. Copyright © by Glencoe/McGraw-Hill 4. Two negative charges of 24 C each are separated by 6.0 cm. What force exists between the charges? 5. Two charged spheres are separated by 315 mm. What is the force between them if the charge on one sphere is 9.6 107 C and the charge on the other sphere is 2.2 105 C? 6. Determine the electrostatic force of attraction between a proton and an electron that are separated by 7.5 108 m. 9. Two identical point charges exert a repulsive force of 6.0 103 N when separated by a distance of 6.5 cm. Calculate the charge of each. 10. Two positively charged spheres, A and B, are separated by 0.25 m. The charge on sphere A is one third the charge on sphere B. Find the charge on each sphere if the force of repulsion is 125 N. 11. Three particles are placed in a straight line. The left particle has a charge of 2.0 105 C, the middle particle has a charge of 4.0 106 C, and the right particle has a charge of 3.0 105 C. The left particle is 56 mm from the middle particle and the right particle is 42 mm from the middle particle. Find the net force on the left particle. 12. A positive charge of 23 C is 15 cm directly north of a positive charge of 38 C. A third positive charge of 71 C is 45 cm directly west of the 38-C charge. Determine the net force on the 38-C charge. Physics: Principles and Problems Supplemental Problems • Chapter 20 37